Hormones to Treat Cryptorchids

While giving hormones to colts might seem like a method of self-destruction, there really is a reason for it in some cases--such as for cryptorchids. These colts have at least one testicle that hasn't descended into the scrotum; normally this occurs by 10 days after birth. James Brendemuehl, DVM, PhD, Dipl. ACT, assistant professor of veterinary clinical medicine at the University of Illinois-Urbana, discussed a study using human chorionic gonadotropin (hCG) to influence testosterone production and testicular descent in 16 Thoroughbred colts.

During his presentation at the 52nd annual American Association of Equine Practitioners Convention, held Dec. 2-6, 2006, in San Antonio, Texas, Brendemuehl explained that hCG is "routinely used in prepubertal boys to facilitate testicular descent of inguinally retained testes. The goals of this study were to compare the endocrine (hormone) response of prepubertal colts with descended or cryptorchid testicles to repeated hCG administration, and to determine whether hCG treatment influences testicular descent."

Six colts had both testes descended, while 10 had only one testicle descended (two had the testicle retained in the abdomen, while the retained testicle was just above the inguinal ring in the other eight colts). All 16 colts, which were 180-240 days old, received 2,500 IU hCG via intramuscular injection twice weekly for four weeks.

While testosterone was undetectable in all colts before treatment, all responded with a significant increase in testosterone production. Brendemuehl noted that this response was comparable to that of adults. The cryptorchid colts had lower levels of testosterone (78.5 pg/mL) than colts with both descended testicles (132.5 pg/ml), but this number was not significant, possibly due to the small number of colts in the study. Testicular volume was slightly higher after treatment, but this was also not statistically significant.

Last but certainly not least, half of the colts with testes retained above the inguinal ring had those testes descend after treatment.

"While it is possible that delayed descent could and does occur spontaneously in certain individuals, such as colts with enlarged inguinal rings, this has not been supported by well-documented case reports," commented Brendemuehl. "It is therefore unlikely that testicular descent would have occurred in 50% of the treated group without HCG administration.

"Additional studies are necessary to determine if early hormone intervention in prepubertal cryptorchid colts minimizes Sertoli cell degeneration (which has been shown in cryptorchid boys) and improves subsequent fertility," he concluded. "The genetic implications of cryptorchidism in horses are poorly characterized and highly controversial."

Get research and health news from the American Association of Equine Practitioners 2006 Convention in The Horse'sAAEP 2006 Wrap-Up sponsored by OCD Equine. Files are available as free PDF downloads.

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